Creating a form that checks for Data entry

[TLCTech]

I am trying to create a form with Access 2013. I need to check the table data that has been previously entered to see when the last entrance date and exit date was when they were entered into the table. I then need to check to see if their stay that was entered is 14 days. Another thing that I need to check is if they have stayed with us 14 days in the last 30 days. If they have not, how many days do they have left to stay. If they did, tell me that they cannot stay. Any help would be appreciated. I am new to database.

[June7]

This could get complicated.

Entrance and exit dates are in the same record?

Build a query that calculates the length of the visit - use DateDiff function to construct this calculated field in query - and also pulls the most recent (as defined by the exit date?) record for each entity (client, guest, customer ?). Review http://allenbrowne.com/subquery-01.html#TopN

Get that much working first.